BMI Calculator — Body Mass Index
Discover your Body Mass Index and whether your weight is healthy according to World Health Organization criteria. Free, no registration.
Enter your data to see the result
You will get your WHO category, healthy weight, scale bar and recommendations based on your sex.
Healthy weight
Goal
Clinical Guide
What is the Body Mass Index?
The Body Mass Index (BMI) is the international reference indicator for assessing body weight relative to height, adopted by the WHO as the world public health standard.
Definition
Desarrollado por Adolphe Quetelet en el siglo XIX, el IMC estima la grasa corporal a partir del peso y la altura. La OMS lo adoptó como herramienta estándar de cribado en salud pública.
Calculation Formula
BMI =
weight (kg)
height² (m)
Ex: 70 kg ÷ 1.75² m = 22.9
Clinical Utility
Herramienta de cribado para identificar categorías de peso asociadas a mayor riesgo de enfermedades cardiovasculares, diabetes tipo 2 y otras patologías metabólicas crónicas.
WHO Classification
BMI Categories Table
Official WHO classification valid for adults aged 18 and over. Includes BMI range, risk level and associated health status.
| Category | BMI (kg/m²) | Risk |
|---|---|---|
| Underweight | < 18,5 | Moderate |
| Normal weight | 18,5 – 24,9 | Low |
| Overweight | 25,0 – 29,9 | Increased |
| Obesity I | 30,0 – 34,9 | High |
| Obesity II | 35,0 – 39,9 | Very high |
| Obesity III | ≥ 40,0 | Extreme |
Physiological differences
BMI in men and women
WHO ranges are identical for both sexes, but body composition and fat distribution present relevant physiological differences.
Men
Healthy BMI: 18.5 – 24.9
- Higher proportion of muscle mass, which can raise BMI without indicating excess fat.
- Predominantly abdominal fat distribution (android pattern), with greater associated cardiovascular risk.
- Healthy body fat percentage: 8–24%. In highly muscular men, complement with bioimpedance.
Women
Healthy BMI: 18.5 – 24.9
- Higher body fat percentage physiologically (20–35% healthy), essential for hormonal and reproductive functions.
- Peripheral distribution (hips, thighs) with lower cardiovascular risk than the abdominal pattern.
- After menopause, fat redistributes towards the abdomen, increasing metabolic risk even when BMI appears normal.
Clinical context
BMI Limitations
BMI is a population screening tool, not an individual diagnosis. Interpret results in their appropriate context.
01
Does not measure fat directly
BMI does not distinguish between muscle and fat tissue. It reflects the weight/height ratio, but not actual body composition.
02
Athletes and sportspeople
High muscle mass raises BMI without excess fat. For athletes, bioimpedance or skinfold measurements are recommended.
03
Age and composition
With ageing, muscle mass is lost and fat accumulates. BMI may appear normal with an unfavourable body composition.
04
Visceral abdominal fat
Intra-abdominal fat is the strongest predictor of cardiovascular risk. Waist circumference complements BMI in this assessment.
05
Ethnic variability
For Asian populations, risk begins at BMI ≥23 (overweight) and ≥27.5 (obesity), per specific WHO recommendations.
06
Adults only
For those under 18, age- and sex-adjusted percentiles are used. This tool is designed exclusively for adults.
Clinical note
BMI is a guideline indicator and does not replace individualised medical evaluation. If you have concerns about your weight or body composition, always consult your doctor or registered nutritionist.
Frequently asked questions
All About BMI
Evidence-based answers to the most common questions about BMI, ideal weight and body health.
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